Tree harvester assembly

ABSTRACT

A tree harvester assembly ( 5 ) has a pivoting tower ( 10 ) which secures the trunk ( 7 ) of the tree ( 8 ) and may pivot to impart a bending moment upon the tree ( 8 ), thereby permitting easier cutting by a chain saw ( 205 ). The tree harvester ( 5 ) also has a pivot chain saw guide ( 200 ) which permits the harvester ( 5 ) to cut trees on a hillside at an orientation parallel to the terrain of the hillside at a low stump height. The tree harvester ( 5 ) also has clamping arms ( 405, 410 ) which may be selectively pivoted to secure a tree ( 8 ) against the tower ( 10 ) and to selectively release the tree ( 8 ) in one direction or another. A chain saw pivoting and drive apparatus ( 600 ) permits the chain saw ( 205 ) to be pivoted about a desired range and simultaneously driven to perform a cutting operation. Finally, the tree harvester assembly ( 5 ) includes a chain saw tensioning device ( 800 ) utilizing floating dovetails ( 810 ) urged apart by a spring element ( 805 ) which acts to urge the chain ( 612 ) of the chain saw ( 205 ) away from the drive sprocket ( 627 ), thereby tensioning the chain ( 612 ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention is directed to an apparatus for harvesting trees wherebythe trunk of a tree is grasped and a chain saw severs the trunkproximate to its base.

2. Description of Related Art

Tree harvesting involves the removal of trees by cutting so that thetree may be processed for industrial or commercial applications. Acommon problem while cutting trees occurs as a chain saw enters thefinal phase of cutting. In particular, as a chain saw removes materialto produce a groove within the tree, the saw advances through the treeand the remaining portion of the tree in front of the chain saw isincapable of supporting the entire weight of the tree. For that reason,the tree begins to tilt and to pinch the chain saw. It is fairly commonfor a chain saw to stall and, to overcome this hurdle, the chain saw maybe oversized such that it has surplus power to continue operating evenafter the tree pinches the saw. As a result, larger chain saws are usednot because of the difficulty in penetrating the wood of the tree, butto overcome the friction caused by the tree when it pinches upon the sawblade.

Additionally, it is important to maintain the chain of the chain saw atthe proper tension to insure proper operation. Some prior artarrangements adjust the tension of the chain when the chain is hot suchthat, upon cooling, the chain retracts at a greater rate than the chainbar, thereby putting excessive tension upon the chain which may causedamage to either the chain or the chain bar.

Additionally, many tree harvesting machines secure the trunk of a treewithin a tower utilizing interlocking clamps. As a result, when it isnecessary to release the tree, all the clamps must be simultaneouslyreleased which permits little or no flexibility in selecting thedirection in which the tree trunk will far.

SUMMARY OF THE INVENTION

The subject invention is directed to a tree harvester having a pivotingsecuring tower, a pivoting chain saw guide, an arrangement to secure atree trunk within the tower, a chain saw pivoting/driving apparatus, anda chain saw tensioning device.

One aspect of the invention is an apparatus for cutting trees tocomplement the operation of a chain saw, wherein the apparatus issupported upon a structure and wherein the apparatus comprises:

-   -   a) a chain saw guide secured to the structure, wherein the guide        has:        -   1) an opening adapted to accept a tree trunk,        -   2) a generally planar bottom surface adapted to rest upon            the terrain; and        -   3) a chain saw pivotally mounted to the guide about an axis            to traverse the entire opening along a plane parallel to the            planar bottom surface from a starting cut position to a            finishing cut position, wherein the starting cut position            defines a starting cut point and wherein the finishing cut            position defines a finishing cut point;    -   b) a securing tower for selectively securing and releasing the        tree trunk, wherein        -   1) the securing tower has a centerline extending along its            length,        -   2) the securing tower is pivotally supported by a tower            pivot mounted upon the structure to provide rotation about a            tower pivot axis, and        -   3) the tower pivot axis is located above and offset in a            direction away from the finishing cut point, such that a            tree trunk secured within the tower will be urged upward and            away from the finishing cut point when the tower is pivoted            away from the chain saw guide.

Another aspect of the invention is an apparatus for cutting trees on asloping terrain, wherein the apparatus is supported upon a structure,wherein the apparatus comprises:

-   -   a) a chain saw guide pivotally connected to the structure,        wherein the chain saw guide has an opening to accept a tree        trunk, a generally planar bottom surface adapted to rest upon        the terrain and a chain saw pivotally mounted to the guide to        traverse the entire opening along a plane parallel to the planar        bottom surface from a starting cut position to a finishing cut        position, wherein the starting cut position defines a starting        cut point and wherein the finishing cut position defines a        finishing cut point, and    -   b) securing tower for selectively securing and releasing the        tree trunk.

Another aspect of the invention is an apparatus for securing treesduring and after a cutting operation using a chain saw, wherein theapparatus is supported upon a structure and wherein the apparatuscomprises:

-   -   a) a securing tower adapted to secure a tree trunk therein,        wherein the tower has an upper end and a lower end, which define        the length and wherein the tower further has a first side, a        second side and a rear side;    -   b) a stabilizer at the upper end of the tower,    -   c) at least one clamping arm on each the first side and the        second side of the tower, wherein each arm is spaced from the        other arm and each bar is positioned at a different location        along the length of the tower and wherein at least one clamping        arm may independently pivot from an open position to a closed        position suitable to embrace the tree against the tower or        release the tree from the tower, and    -   d) at least one blade protruding from the rear side of the        tower, wherein the blade has an edge adapted to penetrate a tree        trunk when the tree is embraced within the tower.

Yet another aspect of the invention is a tensioning apparatus for achain on a chain saw comprising:

-   -   a) a base with a drive sprocket rotatingly mounted therein about        an axis;    -   b) a chain saw bar secured to a chain support and slidingly        mounted to the base in a direction radial to the sprocket axis,        wherein the bar has an outer rim;    -   c) a chain supported by a chain support and attached to the        drive sprocket and engaged and guided to slide over the outer        rim of the chain saw bar; and    -   d) a biasing element, which urges the chain saw bar in the        radial direction away from the sprocket, thereby imparting a        tension to the chain.

Yet another aspect of the invention is an apparatus for radiallypivoting and driving a chain saw comprising:

-   -   a) a base having a cylindrical bore extending therethrough about        an axis;    -   b) a cylindrical hub rotatingly mounted within the bore of the        base about the axis, wherein the hub has a cylindrical bore        extending therethrough, wherein the chain saw is mounted upon        the exterior of the cylindrical hub;    -   c) a drive shaft extending through and rotatably supported        within the bore of the hub about the axis;    -   d) a hub drive mechanism for rotating the cylindrical hub        through a range of rotational motion about the axis, wherein the        chain saw is thereby pivoted through the same range of        rotational motion; and    -   e) a chain drive mechanism for rotating the drive sprocket on        the chain saw to drive the chain.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a front view of the tree harvester in accordance with thesubject invention;

FIG. 2 is a side view of the tree harvester in accordance with thesubject invention;

FIG. 3 is a top view of the tree harvester in accordance with thesubject invention;

FIG. 4 is a schematic of the side view of the tree harvester inaccordance with the subject invention illustrating the pivotal motion ofthe tower;

FIG. 5 is a schematic of the side view of the tree harvester inaccordance with the subject invention illustrating the pivotal motion ofthe chain saw guide;

FIG. 6 is a schematic of the side view of the tree harvester inaccordance with the subject invention further illustrating the pivotalmotion of the tower;

FIG. 7 is a top view of the chain saw guide;

FIG. 8 is a schematic side view illustrating details of the mechanism torotationally orient and to drive the chain saw; and

FIG. 9 is a perspective view of the arrangement illustrated in FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1-3 illustrate a front, side and top view of the tree harvester inaccordance with the subject invention. The subject invention will bedescribed in the context of five aspects, which include:

-   -   1) a pivoting securing tower 10;    -   2) a pivoting chain saw guide 200 (FIG. 2);    -   3) an arrangement 400 to secure a tree trunk within the tower 10        (FIG. 3);    -   4) a chain saw pivoting/driving apparatus 600 (FIG. 8); and    -   5) a chain saw tensioning device 800 (FIG. 8).

As a brief overview, the tree harvester 5 is positioned, as illustratedin FIG. 1, such that the securing tower 10 is adjacent to the trunk 7 ofa tree 8. Clamping arms 405, 410 pivot inwardly to embrace the trunk 7against the securing tower 10. A chain saw 205 (FIG. 2) is pivotedacross the path of the trunk 7, thereby severing the trunk 7 from thebase 9 of the tree. The trunk 7 is then moved by the securing tower 10and deposited at a location suitable for further processing.

Redirecting attention to FIGS. 1-3, in one aspect of the subjectinvention, the tree harvester 5 includes an apparatus for cutting treesto complement the operation of a chain saw 205. In particular, the treeharvester 5 is mounted upon a structure 15, which for purposes of ourdiscussion, will be considered to be stationary unless specifiedotherwise. In a typical application, the structure 15 may be mountedupon a construction vehicle such as a bulldozer capable of supportingthe entire weight of the tree harvester 5 so the tree harvester 5 may betransported and positioned around trees slated for removal. However, thestructure 15 is intended only to illustrate a means of supporting andmanipulating the tree harvester 5.

The tree harvester 5 is comprised of a chain saw guide 200 secured tothe structure 15. The chain saw guide 200, as illustrated in FIGS. 2 and3, has an opening 210 to accept a tree trunk 7. The chain saw guide 200additionally has a generally planar bottom surface 213 adapted to restupon terrain adjacent to the tree 8. The chain saw guide 200 has a chainsaw 205 (FIG. 2) mounted to the guide 200 about an axis 215 (FIG. 2) totraverse the entire opening 210 along a plane 217 parallel to the planarbottom surface 213 from a starting cut position to a finishing cutposition, wherein the starting cut position occurs when the chain saw205 first contacts the tree trunk 7 to define a starting cut point 220and, wherein the finishing cut position occurs as the chain saw 205passes through the last portion of remaining material, thereby defininga finishing cut point 23.

The securing tower 10 of the tree harvester 5 is for selectivelysecuring and releasing the tree trunk 7. The securing tower 10 has acenterline 13 extending along its entire length. The securing tower 10is pivotally supported by a tower pivot 17 mounted upon the structure 15to provide rotation about a tower pivot axis 20. The tower pivot axis 20is located above and offset in a direction away from the finishing cutpoint 23 when the securing tower 10 is pivoted away from the chain sawguide 200. Such an arrangement is schematically illustrated in FIG. 4.

This feature permits nearly unencumbered advancing of the chain saw 205through the tree trunk 7 since the tree trunk 7, when secured by thetower 10, may be lifted up and away from the trunk 7 to substantiallyreduce or eliminate pinching by the weight of the tree 8 that wouldnormally rest upon the chain saw 205.

This feature provides a number of benefits. First of all, since thechain saw 205 may pass unencumbered through the trunk of the treewithout the need for increased power to overcome frictional forcesgenerated when the tree pinches against the chain saw, then the chainsaw may become smaller in size, weight and power. Additionally, withoutthe weight of the tree trunk bearing upon the chain saw, the wear andtear upon the chain saw is substantially reduced.

While the securing tower 10 may be pivotally supported about the towerpivot 17, the chain saw guide 200 may also be pivotally supported by achain saw guide pivot 225 mounted upon the structure 15 to providerotation about a chain saw guide pivot axis 227. It should beappreciated that the securing tower 10 in one embodiment does not restdirectly upon the structure 15, but that the chain saw guide 200 acts asan intermediate member between the tower 10 and the structure 15. Inthis fashion, it is possible to pivot the tower 10 and to pivot thechain saw guide 200 with the understanding that whenever the chain sawguide 200 pivots, the pivot 17 of the securing tower 10 is displacedalong its arc 24 (FIG. 4) defined by a radius from the chain saw guidepivot 225 and the tower pivot 17. The chain saw guide pivot 225 islocated below and away from the tower pivot 17 in a direction away fromthe finishing cut point 23.

FIG. 5 illustrates the chain saw guide 200 pivoted in an upward positionwith the tower 10 in a vertical position, while FIG. 6 illustrates thechain saw guide 200 in a horizontal position with the tower 10 tiltedforward. While in a typical application, the tower 10 will most likelynot be tilted to the same degree illustrated in FIG. 6, this isillustrated only to show the manner in which the tower 10 may pivot.

Briefly returning to FIG. 5, it should be noted that when the chain sawguide 200 is angled upwardly, while the location of the chain saw guidepivot 225 does not change, the location of the tower pivot 17 moves upand to the right, thereby slightly reorienting the tower 10.

The pivoting securing tower 10 and the pivoting chain saw guide 200 bothserve different purposes, however, may be used in combination with oneanother to provide increased versatility.

In particular, it is not uncommon for the terrain adjacent to a tree tobe slightly higher than the ground away from the tree. Under thesecircumstances, the chain saw guide 200 may pivot upward to accommodatethis raised surface without the need to elevate the structure 15 at thesame time. Additionally, for trees located upon an uneven terrain, thechain saw guide may pivot to conform to the terrain without requiringthe structure 15 to also conform to the terrain. As an example, if abulldozer was supporting the structure 15 and was advancing forward tothe base of a hill where a tree was located, with the bulldozer stilloriented horizontally at the base of the hill, the chain saw guide 200may pivot to accommodate the terrain of the hillside. This not onlypermits easier operation of the tree harvester but, furthermore, thechain saw 205 (FIG. 2), since it cuts a path parallel to the bottom ofthe chain saw guide 200, will sever the tree along a path generallyparallel to the ground. In other prior art tree harvesters, the chainsaw blade was not pivotable and, as a result, the cut of the tree wasrequired at a higher position so that the chain saw would not be forcedinto dirt adjacent to the tree on the upper hillside of the tree.Cutting the tree to provide a lower stump also provides a significantsafety advantage to the operator of the tree harvester since frequentlythe vehicle supporting the tree harvester must travel in reverse and, ifa tree stump is cut low, there is less concern that the vehicle drivenby the operator will be stopped by or tipped by a protruding stump. Forthese reasons, the pivotable chain saw guide 200 is advantageous overthe teaching of the prior art.

Directing attention to the securing tower 10, a hydraulic cylinder 25 issecured between the structure 15 and the tower 10 to manually displacethe tower 10 about the tower pivot 17. This manipulation provides asignificant advantage during a cutting operation since, as illustratedin FIG. 4, the tower 10 is capable of being tilted rearwardly away fromthe cut of a chain saw 205, thereby relieving the weight of the tree 8from the chain saw blade and permitting free, unencumbered cutting bythe chain saw 205. Additionally, as will be discussed further, the tower10 may be tilted forward and the clamping arms 405, 410 may beselectively manipulated to release the trunk of the tree in apreselected direction.

While each of these pivoting features are beneficial unto themselves, asillustrated in the figures, in a preferred embodiment, the tower pivot17 rests upon the chain saw guide 200 which itself, through the chainsaw pivot 225, pivots about the structure 15. As illustrated in FIG. 4,it is important for the finishing cut point 223 to be distant from thetower pivot 17, such that when the tower 10 rotates, the tree 8 is notonly urged in a bent position relative to the trunk 7, but is alsolifted upwardly relative to the trunk 7.

The tower pivoting device 25 may be a hydraulic cylinder, however, itshould be appreciated that any number of devices capable of rotating thetower 10 about the tower pivot 17, would be suitable.

The chain saw guide 200 is not significantly affected by the operationof the hydraulic cylinder 25 and, as a result, may move freely up anddown. In order to prevent gravity from displacing the chain saw guide200 outside of its range of motion, the chain saw guide 200 is linked tothe tower 10, utilizing a chain 27. The length of the chain 27 isadjustable to orient the chain saw guide 200 in a desired angularorientation, such as, for example, the orientation illustrated in FIG.5.

While so far the discussion has indicated that a tree trunk may besecured within the tower, the apparatus for accomplishing such a taskwill now be discussed.

Again directing attention to FIGS. 1-3, the details of the arrangementto secure a tree trunk will be described. The securing tower 10 isadapted to secure a tree trunk 7 wherein the tower has an upper end 412and a lower end 415 defining a length therebetween. Furthermore, thetower has a first side 417, a second side 420, and a rear side 422. Astabilizer 425 is generally U-shaped for surrounding a portion of thetree trunk 7. A pivotable clamping arm 405 may have a generally C-shapedconfiguration and is pivotally attached to the first side 417 of thetower 10. The clamp 405 may be pivoted to secure the tree trunk 7 withinthe stabilizer 425 against the tower 10. Similarly, a clamping arm 410is pivotally mounted to the second side 420 of the tower 10 andgenerally C-shaped such that it may embrace the tree trunk 7 against thetower 10;

It is important to note that both clamping arm 405 and clamping arm 410are spaced apart from each other along the length of the tower 10 suchthat, in their closed position, they do not overlap with one another.Each clamping arm may independently pivot from an open position to aclosed position suitable to embrace the tree trunk 7 against the tower10 or release the tree trunk 7 from the tower 10. A plurality of blades428, 430 protrude from the rear side 422 of the tower 10, wherein eachblade 428, 430 has an edge adapted to penetrate the tree trunk 7 whenthe tree is embraced within the tower 10. While it may be possible thatthe force of the clamping arms 405, 410 against the tree trunk 7 withinthe tower 10 would be sufficient to prevent vertical displacement of thetrunk 7 within the tower 10, the introduction of the blades 428, 430ensures that the clamped tree trunk 7 will not be vertically displacedwithin the tower 10. There may be an additional blade 431 associatedwith the chain saw guide 200 to secure the bottom of the trunk 7.

Clamping arm 432 is mounted to the first side 417 of the tower 10 in astationary position. While clamping arm 432 may also be pivotable,inasmuch as it provides an opposing force to clamping arm 410 to furtherstabilize the tree trunk 7, then it is not imperative for it to bepivotable. Nevertheless, it may be pivotable, thereby providing theoperator with greater flexibility in releasing the tree. The clampingarms 405, 410, since they may independently pivot from an open positionto a closed position, may selectively embrace the tree or release thetree in a controlled fashion to cause it to fall in a particulardirection.

The pivotable clamping arms 405, 410 are each operated by a dedicateddrive device illustrated schematically by items 435, 437. The dedicateddrive device 435, 437 for each pivotable clamping arm, 405, 410 may bean electric motor and, furthermore, the electric motor may be used inconjunction with a self locking reduction gear unit. A self-lockingreduction gear unit remains in the last position it assumed when themotor was de-energized.

It is possible that one or more of the pivotable clamping arms 405, 410be comprised of two or more extensions, as illustrated by extensions440, 442 on clamping arm 405. It is also possible to have a singleextension on clamping arm 405 which has the same width as the combinedextensions 440, 442. However, with the occurrence of multiple extensions440, 442 on each clamping arm, it is important that the clamping arms405, 410 remain spaced apart along the length of the tower such that theadjacent clamping arms are positioned in a non-overlapping fashion.

The subject tree harvester utilizes an apparatus for radially pivotingand driving a chain saw. Directing attention to FIG. 2 as an overview,the chain saw pivoting and driving apparatus is encircled and identifiedas reference item 600. This apparatus 600 is used to both drive thechain 612 of the chain saw 205 and also to radially orient the chain sawover the range of rotation necessary to sever the trunk of a tree beingheld within the tower 10. The chain saw pivoting/driving apparatus 600rests upon the chain saw guide 200, as illustrated in FIGS. 1, 2 and 8.Directing attention to FIGS. 7-9, the apparatus 600 is comprised of abase 605 having a cylindrical bore 607 extending therethrough. The chainsaw 205 comprised of a bar 610 and a chain 612, is mounted upon theexterior of a cylindrical hub 615 rotatingly mounted within the bore 607of the base 605.

A drive shaft 617 extends through and is rotatably supported within acylindrical bore 620 extending through the cylindrical hub 615. A hubdrive mechanism 622 rotates the cylindrical hub 615 through a range ofrotational motions about axis 618, thereby carrying the chain saw 205and pivoting the chain saw 205 through the same range of rotationalmotion. A chain drive mechanism 625 rotates a drive sprocket 627 on thechain saw 205 to drive the chain 612.

The hub drive mechanism 622, in one embodiment, is comprised of a drivenpulley 630 mounted to a portion of the cylindrical hub 615 and a driverpulley 632 mounted to a motor 635 secured to the base 605, wherein thedriver pulley 632 engages the driven pulley 630 through belt 633 topivot the chain saw 205 within the desirable range. The hub drivemechanism is illustrated as a belt-driven pulley arrangement in FIG. 8.FIG. 9 illustrates a gear driven system wherein a driver gear 632engages a driven gear 630. It is entirely possible to provide a hubdrive mechanism which uses other known hardware, such as chain drivensprockets instead of meshing gears or a pulley arrangement. Brieflydirecting attention to the FIG. 7, the range of rotation of the chainsaw 205 is illustrated by angle 37, which is approximately 180°.

The motor 635 may be an electric motor and, furthermore, may be anelectric motor having braking capability. In particular, a motor havingbraking capability is one that when in a de-energized state will retainthe last position of the energized state.

As mentioned, with reference to FIG. 7, the chain saw 205 may pivot overa range indicated by angle 37. Oftentimes, the chain saw operator usinga tree harvester or another device utilizing a pivoting chain saw maynot be able to see the chain saw in operation and, therefore, may notknow the position of the chain saw relative to a piece being cut. Forthat reason, the present invention utilizes sensors to identify therotational position of the cylindrical hub 615 and the attached chainsaw 205. In particular, in one embodiment, a plurality of sensors 640A,B, C, D (FIG. 9) may be mounted upon the driven gear 630 with one ormore opposing sensors 642 mounted upon the base 605 capable of recordingthe rotational position of the cylindrical hub 615. Such sensors mayconsist of Hall effect sensors, reed switch sensors or mechanicalsensors known by those skilled in the art of measurements.

The cylindrical hub 615 is rotatably secured within the base 605 usingbearings 645, 647 secured at opposite ends of the cylindrical hub 615.

As an additional feature, limit switches 650, 652 (FIG. 7) may beincluded such that, when the chain saw 205 reaches its extreme range ofmotion, the operator will be notified and/or the chain saw will bede-energized.

Briefly returning to FIG. 8, it should be noted that, for illustrativepurposes, the chain 612 (FIG. 9) is not shown. However, the chain isdriven by drive sprocket 627, which is rotated by drive shaft 617, whichitself is rotated by pulley 655, which is turned by belt 657 throughpulley 660 driven by spindle motor 662.

The tree harvester in accordance with the subject invention furtherincludes a chain saw tensioning device 800 (FIGS. 8 and 9) fortensioning the chain 612 on a chain saw 205. The tensioning apparatus800 is comprised of a base 200 with a drive sprocket 627 rotatinglymounted thereon about an axis 618.

The chain saw bar 610 is slidingly mounted to the housing 202 of thebase 200 in a direction radial to the sprocket axis 618. The chain sawbar 610 has an outer rim 611 upon which the chain 612 is guided. Thechain 612 is attached to the drive sprocket 627 and engaged and guidedto slide over the outer rim 611 of the chain saw bar 610. At least onebiasing element 805 urges the chain saw bar 610 in a radial directionaway from the sprocket 627 thereby imparting a tension to the chain 612.

The chain saw bar 610 is slidingly mounted to the housing 202 of thebase 200 through a dovetail configuration 810, 815, wherein one of adovetail projection 812 or dovetail cavity 817 within the base 200engages the other of the dovetail projection 812 or dovetail cavity 817within the chain support 807 which is also the dovetail 815. Dovetail815 is also the chain support 807.

The biasing element 805 may be a compression spring fitted between thehousing 202 of the base 200 and the chain support 807 to urge the chainsupport 807 away from the base 200 such that the tension in the chain612 may be predetermined as a function of the compression spring 805. Inone embodiment, the biasing element 805 may be a compression spring and,furthermore, may be a coil spring. Additionally, the biasing element 805may be one selected from the group consisting of a hydraulic piston anda pneumatic piston.

A locking mechanism 820 may be used to secure the change saw bar 610 ina fixed position relative to the housing 202 of the base 200. Inparticular, the locking mechanism 820 is a friction device thatintroduces friction between the base 200 and the chain saw bars 610 toprevent sliding motion between them. The locking mechanism 820 may becomprised of a rod 822 extending through one of the chain support 807 orhousing 202 of the base 200 and contacting the other to introducefriction between them. The rod 822 is activated to produce friction whenthe chain 612 is in operation and is deactivated to relieve frictionwhen the chain 612 is not in operation. The rod 822 may be controlled byan air operated actuator 825 or other devices known in the art.

In operation, the locking mechanism 820 is released such that dovetail810 and dovetail 815 may slide relative to one another allowing thebiasing element 805 to push the chain bar 610 away from the drivesprocket 627, thereby tensioning the chain 612. At the time ofoperation, the locking mechanism 820 is activated, thereby producingfriction between the dovetail 810 and the dovetail 815 to preventrelative motion between to retain the chain tension 615. Each time thechain saw is de-energized, the locking mechanism 820 is alsode-energized, thereby permitting the chain saw bars 610 to slide withthe dovetail 815 in a fashion permitted by the biasing element 805. Asan example, if during operation, the chain 612 becomes loose, then, atthe time the chain saw is deactivated, the locking mechanism S20 is alsodeactivated, thereby permitting the biasing element 805 to push thechain saw bar 610 away from the drive sprocket 627 to again subject thechain 612 to the predetermined tension determined by the biasing element805. It is necessary to engage the locking mechanism 820 prior toenergizing the chain saw since the forces to which the chain saw will besubjected would in many circumstances cause the chain saw bar 610 to beurged toward the drive sprocket 627, thereby loosening the chain.

While specific embodiments of the invention have been described indetail, it will be appreciated by those skilled in the art that variousmodifications and alternatives to those details could be developed inlight of the overall teachings of the disclosure. The presentlypreferred embodiments described herein are meant to be illustrative onlyand not limiting as to the scope of the invention which is to be giventhe fall breadth of the appended claims and any and all equivalentsthereof.

1. An apparatus for cutting trees to complement the operation of a chainsaw, wherein the apparatus is supported upon a structure and wherein theapparatus comprises: a) a chain saw guide secured to the structure,wherein the guide has 1) an opening adapted to accept a tree trunk, 2) agenerally planar bottom surface adapted to rest upon the terrain, and 3)a chain saw pivotally mounted to the guide about an axis to traverse theentire opening along a plane parallel to the planar bottom surface froma starting cut position to a finishing cut position, wherein thestarting cut position defines a starting cut point and wherein thefinishing cut position defines a finishing cut point; b) a securingtower for selectively securing and releasing the tree trunk, wherein 1)the securing tower has a centerline extending along its length, 2) thesecuring tower is pivotally supported by a tower pivot mounted upon thestructure to provide rotation about a tower pivot axis, and 3) the towerpivot axis is located above and offset in a direction away from thefinishing cut point, such that a tree trunk secured within the towerwill be urged upward and away from the finishing cut point when thetower is pivoted away from the chain saw guide.
 2. The apparatusaccording to claim 1, wherein the chain saw guide is pivotally supportedby a chain saw guide pivot mounted upon the structure to providerotation about a chain saw guide pivot axis.
 3. The apparatus accordingto claim 2, wherein the tower pivot is supported upon the chain sawguide which is supported upon the structure such that when the chain sawguide is pivoted, the tower pivot is displaced along an arc definedbetween the chain saw guide pivot and the tower pivot.
 4. The apparatusaccording to claim 2, wherein the chain saw guide pivot is located belowand away from the tower pivot in a direction away from the finishing cutpoint.
 5. The apparatus according to claim 1, further including a towerpivoting device attached to the support and to the tower for selectivelypivoting the tower.
 6. (canceled)
 7. The apparatus according to claim 5,wherein the chain saw guide is linked to the tower to limit downwardrotation of the chain saw guide.
 8. The apparatus according to claim 7,wherein the chain saw guide is linked to the tower by a chain extendingfrom the tower to support the chain saw guide and thereby limit downwardrotation.
 9. The apparatus according to claim 8, wherein the chainlength is adjustable to orient the chain saw guide in a desired angularorientation.
 10. (canceled)
 11. An apparatus for cutting trees on asloping terrain, wherein the apparatus is supported upon a structure,wherein the apparatus comprises: a) a chain saw guide pivotallyconnected to the structure, wherein the chain saw guide has an openingto accept a tree trunk, a generally planar bottom surface adapted torest upon the terrain and a chain saw pivotally mounted to the guide totraverse the entire opening along a plane parallel to the planar bottomsurface from a starting cut position to a finishing cut position,wherein the starting cut position defines a starting cut point andwherein the finishing cut position defines a finishing cut point, and b)a securing tower for selectively securing and releasing the tree trunk.12. The apparatus according to claim 11, wherein the chain saw guide ispivotally supported by a chain saw guide pivot mounted upon thestructure to provide rotation about a chain saw guide pivot axis. 13-14.(canceled)
 15. The apparatus according to claim 11, further including atower rotation device attached to the support and to the tower forselectively pivoting the tower. 16.-22. (canceled)
 23. A tensioningapparatus for a chain on a chain saw comprising: a) a base with a drivesprocket rotatably mounted therein about an axis; b) a chain saw barsecured to a chain support and slidingly mounted to the base in adirection radial to the sprocket axis, wherein the bar has an outer rim;c) a chain supported by a chain support and attached to the drivesprocket and engaged and guided to slide over the outer rim of the chainsaw bar d) a biasing element, which urges the chain saw bar in theradial direction away from the sprocket, thereby imparting a tension tothe chain.
 24. The tensioning apparatus according to claim 23, whereinthe chain saw bar is slidingly mounted to the base through a dovetailconfiguration and wherein one of a dovetail projection or dovetailcavity within the base engages the other of a dovetail projection ordovetail cavity within the chain support.
 25. The tensioning apparatusaccording to claim 24, wherein the biasing element is a compressionspring fitted between the base and the chain support to urge the chainsupport away from the base, such that the tension in the chain may bepredetermined as a function of the compression spring.
 26. Thetensioning apparatus according to claim 25, wherein the compressionspring is a coil spring.
 27. The tensioning apparatus according to claim23, wherein the biasing element is one from the group consisting of ahydraulic piston and a pneumatic piston.
 28. The tensioning apparatusaccording to claim 23, further including a locking mechanism to securethe chain saw bar in a fixed position relative to the base.
 29. Thetensioning apparatus according to claim 28, wherein the lockingmechanism is a friction device that introduces friction between the baseand the chain saw bar to prevent sliding motion between them.
 30. Thetensioning apparatus according to claim 29, wherein the friction deviceis a rod extending through one of the chain support or the base andcontacting the other to introduce friction between them.
 31. Thetensioning apparatus according to claim 30, wherein the rod is activatedto produce friction when the chain is in operation and is de-activatedto release friction when the chain is not in operation. 32-41.(canceled)
 42. A tree harvester comprising: a) a pivoting securingtower; b) a pivoting chain saw guide; c) an arrangement to secure a treetrunk within the tower; d) a chain saw pivoting/driving apparatus; ande) a chain saw tensioning device.